Nanoscale fibers are widely used in textile, energy, environmental and bioengineering applications as they exhibit unique optical, electrical, mechanical, and biological properties that are not found in their bulk counterparts. Some of these applications require highly ordered, well-aligned fiber architectures in order to provide the required physical, mechanical, chemical or electrical anisotropy. For example, aligned polymer fibers of various compositions are able to regulate cell migration, proliferation, and differentiation, which is critical for tissue engineering. Highly aligned polyfluorene-based nanofibers can increase charge-carrier mobility or enhance photoluminescence in the fiber alignment direction. Composite electrolyte membranes with aligned polyimide-based fibers demonstrate greater proton-conduction for enhanced fuel cell efficiency. Electrospinning has emerged as a simple, flexible, and versatile technique for creating many nanofiber-based materials.
The production of aligned nanofibers by electrospinning is commonly achieved by use of specially-designed fiber collectors, most notably, a fast rotating mandrel collector or a parallel-electrode collector. In a rotating collector configuration, the produced polymer fibers are deposited on and wrapped around a rotating mandrel. The degree of fiber alignment largely depends on the mandrel rotational speed. In a parallel-electrode configuration, the insulating gap (mostly an air gap) between two parallel electrodes serves as the fiber collector, and charged fibers are aligned up across the gap by the electric field near the electrodes that points perpendicularly to the electrode edges; the length of the aligned fibers is limited by the width of the insulating gap. This configuration bears the advantage that the fibers can be easily removed from the collector, but the degree of fiber alignment decreases as the thickness of the fibrous mat increases due to the reduced electric field strength caused by the accumulated charge of the deposited nanofibers. In this system configuration, a centrifugal force disperses a polymer-solvent solution through a capillary, which causes elongation and thinning of the solution jet, and the fiber is produced with no applied voltage.
Despite these exciting advancements, an electro spinning system that is suitable for large-scale production of fibrous structures while retaining a high degree of fiber alignment has yet to be demonstrated. The present invention seeks to fulfill this need and provides further related advantages.